Enumerated values are formal names for a given bit pattern; it is a way to define values, not types. The formal name, however, is only valid for the type it is defined for, not for any other. It is totally valid to have multiple identical enumerated values which have (possibly) totally different bit pattern, as long as each name is used only on a single type.
Note that ''' is perfectly valid (the formal name is a single quote), but '' is not: the parser will continue scanning for the closing quote.